This application claims the priority of German application 197 16 292.4-14, filed in Germany on Apr. 18, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an extrusion arrangement for manufacturing bent workpieces, having an extrusion die which is guided in an extrusion chamber, which compresses material situated in the extrusion chamber and which presses it through a bottom die arranged at a head-side end of the extrusion chamber, at least two bottom die elements being provided which are arranged behind the bottom die in a parallel adjoining manner.
An extrusion arrangement of this type is known from German Patent Document DE 41 31 332 A1. The extrusion arrangement described there comprises a tool core with an adjoining tool jacket which consists of disk-type, assembled jacket parts. The jacket parts, which are fixedly placed upon one another, together with their supplementing duct sections, form a circular-arc-shaped duct. The described division of the tool jacket into individual segments facilitates the manufacturing in that the duct in the individual segments can be premachined and, when all jacket parts are assembled, can then be processed to form the finished product. For producing an internal profile, rods are provided in the case of the known extrusion arrangement which reach into the circular-arc-shaped duct and which expediently also have a curved design.
From European Patent Document EP 0 706 843 A1, an arrangement is known which is used for the manufacturing of curved solid and hollow profiles with complex cross-sections by means of a combination of extruding and bending, the workpiece being bent simultaneously with or immediately after the forming extrusion process by means of a force acting upon the workpiece transversely to the extruding direction. For this purpose, a device generating a transverse force is arranged behind the bottom die viewed in the extruding direction, which device can be pressed against the emerging billet, a bending zone existing in the space between the extrusion surfaces and the outlet zone which is free of contact surfaces.
From German Patent Document DE-AS 11 07 926, a spraying head for extruding is known for manufacturing curved workpieces from thermoplastic material, in the case of which a ram body is arranged spaced from the nozzle outlet of the spraying head, which ram body is constructed as a slider, which is provided with a recess and is guided transversely to the nozzle duct, or as a rotatable ring with an eccentrically situated opening. By the adjustment of this slider or ring with respect to the normal position, the passage cross-section for the emerging thermoplastic mass is changed on one side, which causes a desired speed difference during the exit from the mouthpiece.
From German Patent Document DD-PS 28 365, an extrusion head for extruding presses is known for manufacturing workpieces from ceramic masses which, for reducing a texture formation, consists of several firmly assembled segments whose inside diameter has a partially conical and partially cylindrical construction.
Based on this state of the art, it is an object of the present invention to provide an extrusion arrangement of the initially mentioned type, in the case of which, immediately following the extruding operation, a stretching-bending operation is possible which is as simple and as space-saving as possible and which permits the manufacturing also of complex, spatially bent profiles.
For achieving this object, an extrusion arrangement is provided for manufacturing bent workpieces, having an extrusion die which is guided in an extrusion chamber and which compresses material situated in the extrusion chamber and presses it through a first bottom die arranged at a head-side end of the extrusion chamber, further bottom die elements being provided which are arranged in a parallel adjoining manner behind the first bottom die, wherein the further bottom die elements are displaceably and rotatably disposed such that their successive passage openings form an extrusion duct of a variable curvature and twist.
Accordingly, in preferred embodiments of the invention, further bottom die elements are provided which are arranged behind the bottom die of the extrusion arrangement and which adjoin one another in parallel and with respect to the bottom die. The further bottom die elements are displaceably and rotatably disposed such that their successive passage openings form an extrusion duct whose curvature and twisting are variably and individually adjustable. Preferably, the further bottom die elements can be adjusted continuously and can be fixed in the desired position. Advantageously, the displacement of the bottom die elements takes place in parallel to the bottom die of the extrusion arrangement; that is, perpendicularly to the exiting direction of the extruded profile from the extrusion chamber. The rotating of the further bottom die elements advantageously takes place in a plane in parallel to the plane of the bottom die of the extrusion arrangement; that is, in a plane which is situated perpendicularly to the exiting direction of the extruded profile from the extrusion chamber. According to the invention, the adjoining further bottom die elements therefore form an extrusion duct into which the extruded profile enters after its exiting from the extrusion chamber and the outlet opening of the bottom die. Because of the displaceability and the twisting capacity of the further bottom die elements, the extrusion duct can be provided with an arbitrary curvature and/or a twisting, so that the wall of the extrusion duct formed by the passage openings of the further bottom die elements exercises a transverse force onto the extruded profile.
According to certain preferred embodiments of the invention, the passage openings of the further bottom die elements have rounded edges. As a result, a passage of the extruded profile through the passage openings of the further bottom die elements is ensured without any problem.
In a further development of certain preferred embodiments of the invention, a holding device for the further bottom die elements is provided which is preferably exchangeable so that a different number of bottom die elements can be arranged behind the bottom die of the extrusion device and extrusion ducts of different lengths can therefore be produced.
In a particularly advantageous further development of certain preferred embodiments of the invention, the bottom die of the extrusion arrangement is part of this holding device. As a result, the extrusion arrangement according to the invention has a particularly simple construction and the bottom die can be exchanged without any problems as required.
In a further development of preferred embodiments of the invention, a stationary crosshead of the extrusion arrangement is arranged to be spaced from the further bottom die and from the bottom die elements, for example, by being acted upon by the holding device. For drawing the curved extruded profile off in front of the stationary crosshead, a lateral opening is advantageously provided for this purpose in the holding device.
In order to permit a manufacturing of hollow profiles, in a particularly advantageous further development of certain preferred embodiments of the invention, an arbor is provided in the interior of the extrusion chamber which is arranged essentially concentrically with respect to the exit opening of the bottom die.
So that the hollow cross-section is also maintained in the extrusion duct for bending the billet, the arbor advantageously has an extension which reaches through the exit opening of the bottom die and into the passage openings of the further bottom die elements.
It was found to be particularly advantageous for the extension to consist of a plurality of segments which are movably connected with one another and which are able without any problem to adapt to a curvature defined by the displaceable and rotatable bottom die elements.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.